Telephone



UNITED STATES PATENT OFFICE.

CHARLES STUART BELL, OF COLUMBUS, OHIO.

TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 361,481, dated April 19, 1887.

Application filed October 2, 1886. Serial No. 215,172. (Model.)

.T0 all whom it may concern'.

Be it known that I, CHARLES STUART BELL, of Columbus, in the county of Franklin and State of Ohio, have invented a new and use- `ful Improvement in Telephones, of which the following is a specification.

It is awell-known fact that the two poles of a magnet when combined will sustain by their attractive force many times the weight ot' the magnet, whereas this weight is nearly the limit of the lifting power of a single pole. By use, therefore, of a multipolar magnet the eiiect of the magnetic force on the diaphragm of a telephonie transmitting or receiving instrument may be increased far beyond the de# grec indicated by the sum of the forces which a like number of isolated poles are capable of exerting when taken singly 5 but, for the best effect, the magnetic energy must be concentratedwithin a very narrow iield. In other words, it should be brought to bear as nearly as practicable in the center of the diaphragm. With these principles in View, I have devised and successfully employed an improved form of mnltipolar magnet, whose construction I will proceed to detail by reference to the accompanying drawings, in which- Figure l is a central longitudinal section of a telephonie instrument embodying my improvement. Fig. 2 is a cross section of the compound magnet.

A indicates a permanent bar-magnet, B a soft-iron core, and C a non-magnetic cylinder or sleeve. The permanent magnetA is bored longitudinally, and the soft-iron core B is inserted therein. The cylinder or sleeve C surrounds the latter, B, and is therefore interposed between it and theinclosing permanent magnet A, thus insulating. one from the other. It is made of non-magnetic material, such as brass. The ends of the said parts A B C,

which are contiguous to the diaphragm D, are flush, and constitute either the north or south vpole of the magnet, and the opposite end of the core B is shown reduced and fastened in a corresponding socket formed in the permanent magnet A. A screw, s, is applied to the latter for adjusting the magnet as a whole relative to the diaphragm in the usual way. Surrounding this compound magnet near its 1nner end is a helix, E,with which the conductpoles, as may be demonstrated by the galvanometer. The electrical current traversing 'saidv helix varies the intensity of both the 'north and south poles in this new construction of magnet to such a degree that it far exceeds the power of any other telephonie magnet of which I have knowledge. The force of two magnetic poles is therefore concentrated on the diaphragm at each pulsation of the current. In brief, by the above'described construction and arrangement of part-s A B C, I provide a simple, cheap, and compact form of multipolar magnet which is very efcient in action.

The use of the battery is not requisite with a transmitter or receiver provided with this magnet.

l. The improved mullipolar magnet for use in a telephonie instrument, the same being composed of the permanent magnet A, having a longitudinal bore, the soft-iron core B, inserted therein, and the insulating-cylinder C, made ot' non-magnctic material and surrounding said core, and a helix, applied as shown and described.

2. The combination, with the diaphragm D of a telephonie instrument, of the permanent magnet A, having a longitudinal bore, the softiron core B,inserted therein, the non-magnetic cylinder C, surrounding and therebyin-l CHARLES STUART BELL.

Vitnesses:

S. E. BELL. J. A. KIGHT. 

